Torsional vibrations resulting from engine harmonic excitation are common and lead to excessive noise and reduced gear life, which in turn, may cause premature engine failure. The harmonic excitation is produced by various torques applied to components within the engine, such as a crankshaft or cam shaft, during normal operation. For example, a torque applied to the crankshaft is constantly varied from a high torque, such as when a piston drives the crankshaft down and a low torque, such as when the crankshaft drives the piston upward in a cylinder block. The wide range of torques applied to the crankshaft induce harmonic excitation and torsional vibration in the engine.
Some systems for reducing torsional vibration include inertial masses that, due to centrifugal force, would generally circle the rotation axis of the coupling at the greatest distance possible. Torsional vibrations applied to the coupling cause a pendulum-like relative movement of the inertial masses within the coupling. The frequency of the relative movement can provide resistive inertia torques or provide effective isolation to reduce the torsional vibrations. The use of inertial masses with pendulum-like relative motion in these devices provide a speed sensitive tuning capability that can allow the devices to either track with or avoid engine harmonics as desired when engine speed changes.
U.S. Pat. No. 6,067,876 discloses a system for dampening torsional vibration using rolling bodies as coupling elements, movable relative to a hub disk, a primary flange, and a coverplate, all generally aligned parallel to each other. The hub disk includes cutouts extending in a radial direction. The primary flange and cover plate include matching recesses associated with each hub disk cutout. The cutout and recesses act as guide paths for a coupling body that may move within both the cutout and recesses, allowing deflection of the coupling body due to torsional vibration, thereby dampening vibrations. However, the generally parallel plates disclosed in the '876 patent may not be positioned to readily resist wear from the coupling body that may occur as a result of manufacturing related misalignments. This, in turn, may limit the life of the coupling and subsequently the engine system.
The present disclosure is directed to a system providing torsional vibration attenuation while potentially increasing the system's resistance to wear.